This C++ program is a simple named pipe client that demonstrates the API calls needed to successfully develop a basic named pipe client application. When this application successfully connects to a named pipe, the message “This is a test” is written to the server.
There are four basic steps needed to implement a client:
- Wait for a Named Pipe instance to become available using the WaitNamedPipe() API function.
- Connect to the Named Pipe using the CreateFile() API function.
- Send data to or receive data from the server using the WriteFile() and ReadFile() API functions.
- Close the Named Pipe session using the CloseHandle() API functions.
Compile
cl -o Client Client.cpp
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#include <windows.h> #include <stdio.h> #define PIPE_NAME "\\\\.\\Pipe\\Jim" void main(void) { HANDLE PipeHandle; DWORD BytesWritten; if (WaitNamedPipe(PIPE_NAME, NMPWAIT_WAIT_FOREVER) == 0) { printf("WaitNamedPipe failed with error %d\n", GetLastError()); return; } // Create the named pipe file handle if ((PipeHandle = CreateFile(PIPE_NAME, GENERIC_READ | GENERIC_WRITE, 0, (LPSECURITY_ATTRIBUTES) NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, (HANDLE) NULL)) == INVALID_HANDLE_VALUE) { printf("CreateFile failed with error %d\n", GetLastError()); return; } if (WriteFile(PipeHandle, "This is a test", 14, & BytesWritten, NULL) == 0) { printf("WriteFile failed with error %d\n", GetLastError()); CloseHandle(PipeHandle); return; } printf("Wrote %d bytes", BytesWritten); CloseHandle(PipeHandle); } // // End of client // /*****************************************/ //-----------------------------------------------------------// //OverlappedServer // Module Name: Overlap.cpp // // Purpose: // This sample demonstrates how to develop an advanced named // pipe server that is capable of servicing 5 named pipe // instances. The application is an echo server where data is // received from a client and echoed back to the client. All // the pipe instances are serviced in the main application // thread using Win32 overlapped I/O. // // Compile: // cl -o overlap overlap.cpp // // Command Line Options: // None // #include <windows.h> #include <stdio.h> #define NUM_PIPES 5 #define BUFFER_SIZE 256 void main(void) { HANDLE PipeHandles[NUM_PIPES]; DWORD BytesTransferred; CHAR Buffer[NUM_PIPES][BUFFER_SIZE]; INT i; OVERLAPPED Ovlap[NUM_PIPES]; HANDLE Event[NUM_PIPES]; // For each pipe handle instance, the code must maintain the // pipes' current state, which determines if a ReadFile or // WriteFile is posted on the named pipe. This is done using // the DataRead variable array. By knowing each pipe's // current state, the code can determine what the next I/O // operation should be. BOOL DataRead[NUM_PIPES]; DWORD Ret; DWORD Pipe; for (i = 0; i < NUM_PIPES; i++) { // Create a named pipe instance if ((PipeHandles[i] = CreateNamedPipe("\\\\.\\PIPE\\jim", PIPE_ACCESS_DUPLEX | FILE_FLAG_OVERLAPPED, PIPE_TYPE_BYTE | PIPE_READMODE_BYTE, NUM_PIPES, 0, 0, 1000, NULL)) == INVALID_HANDLE_VALUE) { printf("CreateNamedPipe for pipe %d failed " "with error %d\n", i, GetLastError()); return; } // Create an event handle for each pipe instance. This // will be used to monitor overlapped I/O activity on // each pipe. if ((Event[i] = CreateEvent(NULL, TRUE, FALSE, NULL)) == NULL) { printf("CreateEvent for pipe %d failed with error %d\n", i, GetLastError()); continue; } // Maintain a state flag for each pipe to determine when data // is to be read from or written to the pipe DataRead[i] = FALSE; ZeroMemory( & Ovlap[i], sizeof(OVERLAPPED)); Ovlap[i].hEvent = Event[i]; // Listen for client connections using ConnectNamedPipe() if (ConnectNamedPipe(PipeHandles[i], & Ovlap[i]) == 0) { if (GetLastError() != ERROR_IO_PENDING) { printf("ConnectNamedPipe for pipe %d failed with", " error %d\n", i, GetLastError()); CloseHandle(PipeHandles[i]); return; } } } printf("Server is now running\n"); // Read and echo data back to Named Pipe clients forever while (1) { if ((Ret = WaitForMultipleObjects(NUM_PIPES, Event, FALSE, INFINITE)) == WAIT_FAILED) { printf("WaitForMultipleObjects failed with error %d\n", GetLastError()); return; } Pipe = Ret - WAIT_OBJECT_0; ResetEvent(Event[Pipe]); // Check overlapped results, and if they fail, reestablish // communication for a new client; otherwise, process read // and write operations with the client if (GetOverlappedResult(PipeHandles[Pipe], & Ovlap[Pipe], & BytesTransferred, TRUE) == 0) { printf("GetOverlapped result failed %d start over\n", GetLastError()); if (DisconnectNamedPipe(PipeHandles[Pipe]) == 0) { printf("DisconnectNamedPipe failed with error %d\n", GetLastError()); return; } if (ConnectNamedPipe(PipeHandles[Pipe], & Ovlap[Pipe]) == 0) { if (GetLastError() != ERROR_IO_PENDING) { // Severe error on pipe. Close this // handle forever. printf("ConnectNamedPipe for pipe %d failed with" "error %d\n", i, GetLastError()); CloseHandle(PipeHandles[Pipe]); } } DataRead[Pipe] = FALSE; } else { // Check the state of the pipe. If DataRead equals // FALSE, post a read on the pipe for incoming data. // If DataRead equals TRUE, then prepare to echo data // back to the client. if (DataRead[Pipe] == FALSE) { // Prepare to read data from a client by posting a // ReadFile operation ZeroMemory( & Ovlap[Pipe], sizeof(OVERLAPPED)); Ovlap[Pipe].hEvent = Event[Pipe]; if (ReadFile(PipeHandles[Pipe], Buffer[Pipe], BUFFER_SIZE, NULL, & Ovlap[Pipe]) == 0) { if (GetLastError() != ERROR_IO_PENDING) { printf("ReadFile failed with error %d\n", GetLastError()); } } DataRead[Pipe] = TRUE; } else { // Write received data back to the client by // posting a WriteFile operation. printf("Received %d bytes, echo bytes back\n", BytesTransferred); ZeroMemory( & Ovlap[Pipe], sizeof(OVERLAPPED)); Ovlap[Pipe].hEvent = Event[Pipe]; if (WriteFile(PipeHandles[Pipe], Buffer[Pipe], BytesTransferred, NULL, & Ovlap[Pipe]) == 0) { if (GetLastError() != ERROR_IO_PENDING) { printf("WriteFile failed with error %d\n", GetLastError()); } } DataRead[Pipe] = FALSE; } } } } // // End of OverlappedServer // /*************************/ //--------------------------------------------------------------------------// // Module Name: Server.cpp // // Purpose: // // This program is a simple named pipe server that demonstrates // the API calls needed to successfully develop a basic named // pipe server application. When this application receives a // client connection, it reads the data from the pipe and // reports the received message. // // You need five basic steps to write a named pipe server: // // 1. Create a named pipe instance handle using the // CreateNamedPipe() API function. // 2. Listen for a client connection on a pipe instance using // the ConnectNamedPipe() API function. // 3. Receive from and send data to the client using the // ReadFile() and WriteFile() API functions. // 4. Close down the named pipe connection using the // DisconnectNamedPipe() API function. // 5. Close the named pipe instance handle using the // CloseHandle() API function. // // Compile: // cl -o Server Server.cpp // // Command Line Options: // None // #include <windows.h> #include <stdio.h> void main(void) { HANDLE PipeHandle; DWORD BytesRead; CHAR buffer[256]; if ((PipeHandle = CreateNamedPipe("\\\\.\\Pipe\\Jim", PIPE_ACCESS_DUPLEX, PIPE_TYPE_BYTE | PIPE_READMODE_BYTE, 1, 0, 0, 1000, NULL)) == INVALID_HANDLE_VALUE) { printf("CreateNamedPipe failed with error %d\n", GetLastError()); return; } printf("Server is now running\n"); if (ConnectNamedPipe(PipeHandle, NULL) == 0) { printf("ConnectNamedPipe failed with error %d\n", GetLastError()); CloseHandle(PipeHandle); return; } if (ReadFile(PipeHandle, buffer, sizeof(buffer), & BytesRead, NULL) <= 0) { printf("ReadFile failed with error %d\n", GetLastError()); CloseHandle(PipeHandle); return; } printf("%.*s\n", BytesRead, buffer); if (DisconnectNamedPipe(PipeHandle) == 0) { printf("DisconnectNamedPipe failed with error %d\n", GetLastError()); return; } CloseHandle(PipeHandle); } // // End of Server // /*********************/ //------------------------------------------------------------------------------// // // Thread Server // // Module Name: Threads.cpp // // Purpose: // This sample demonstrates how to develop an advanced named // pipe server that is capable of servicing 5 named pipe // instances. The application is an echo server where data is // received from a client and echoed back to the client. All // the pipe instances are serviced using threads. // // Compile: // cl -o Threads Threads.cpp // // Command Line Options: // None // #include <windows.h> #include <stdio.h> #include <conio.h> #define NUM_PIPES 5 DWORD WINAPI PipeInstanceProc(LPVOID lpParameter); void main(void) { HANDLE ThreadHandle; INT i; DWORD ThreadId; for (i = 0; i < NUM_PIPES; i++) { // Create a thread to serve each pipe instance if ((ThreadHandle = CreateThread(NULL, 0, PipeInstanceProc, NULL, 0, & ThreadId)) == NULL) { printf("CreateThread failed with error %\n", GetLastError()); return; } CloseHandle(ThreadHandle); } printf("Press a key to stop the server\n"); _getch(); } // // Function: PipeInstanceProc // // Description: // This function handles the communication details of a single // named pipe instance. DWORD WINAPI PipeInstanceProc(LPVOID lpParameter) { HANDLE PipeHandle; DWORD BytesRead; DWORD BytesWritten; CHAR Buffer[256]; if ((PipeHandle = CreateNamedPipe("\\\\.\\PIPE\\jim", PIPE_ACCESS_DUPLEX, PIPE_TYPE_BYTE | PIPE_READMODE_BYTE, NUM_PIPES, 0, 0, 1000, NULL)) == INVALID_HANDLE_VALUE) { printf("CreateNamedPipe failed with error %d\n", GetLastError()); return 0; } // Serve client connections forever while (1) { if (ConnectNamedPipe(PipeHandle, NULL) == 0) { printf("ConnectNamedPipe failed with error %d\n", GetLastError()); break; } // Read data from and echo data to the client until // the client is ready to stop while (ReadFile(PipeHandle, Buffer, sizeof(Buffer), & BytesRead, NULL) > 0) { printf("Echo %d bytes to client\n", BytesRead); if (WriteFile(PipeHandle, Buffer, BytesRead, & BytesWritten, NULL) == 0) { printf("WriteFile failed with error %d\n", GetLastError()); break; } } if (DisconnectNamedPipe(PipeHandle) == 0) { printf("DisconnectNamedPipe failed with error %d\n", GetLastError()); break; } } CloseHandle(PipeHandle); return 0; } |
